Perspectives on the First Billion Years of Lunar Evolution from Spacecraft Observations

Impact bombardment is the primary process that shaped the surfaces of solid planetary bodies during earliest evolution. Observations of the Lunar Orbiter Laser Altimeter (LOLA), an instrument on the Lunar Reconnaissance Orbiter, has collected over 7 billion measurements of lunar topography representing the most accurate global topography model for any planet. The observations enable significant advances in analyses of relative ages and degradation states of planetary surfaces, as well as the role of major impacts in the planetary energy budget. Topography combined with high-resolution gravity measurements from the Gravity Recovery and Interior Laboratory (GRAIL) mission are providing unprecedented information on the role of impacts in shaping the lunar crust.